Re: [KJ][PATCH] Correct misc_register return code handling in several drivers

[Neil Horman <nhorman@tuxdriver.com>]

On Tue, Oct 24, 2006 at 01:34:34PM +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2006-10-23 at 13:19 -0400, Neil Horman wrote:
> > Hey All-
> > 	Janitor patch to clean up return code handling and exit from failed
> > calls to misc_register accross several modules.
> 
> The patch doesn't match the description... What are those INIT_LIST_HEAD
> things ? Is this something I've missed or is this a new requirement for
> all misc devices ? Can't it be statically initialized instead ?
> 

The INIT_LIST_HEAD is there to prevent a potential oops on module removal.
misc_register, if it fails, leaves miscdevice.list unchanged.  That means its
next and prev pointers contain NULL or garbage, when both pointers should contain
&miscdevice.list. If we don't do that, then there is a chance we will oops on
module removal when we do a list_del in misc_deregister on the moudule_exit
routine.  I could have done this statically, but I thought it looked cleaner to
do it with the macro in the code.

Thanks & Regards
Neil

> > Thanks & Regards
> > Neil
> > 
> > Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> > 
> > 
> >  drivers/char/mmtimer.c          |   29 +++++++++++++++++++++++------
> >  drivers/char/tpm/tpm.c          |    1 +
> >  drivers/input/misc/hp_sdc_rtc.c |    6 +++++-
> >  drivers/macintosh/apm_emu.c     |    5 ++++-
> >  drivers/net/tun.c               |    2 ++
> >  fs/dlm/user.c                   |    1 +
> >  6 files changed, 36 insertions(+), 8 deletions(-)
> > 
> > 
> > diff --git a/drivers/char/mmtimer.c b/drivers/char/mmtimer.c
> > --- a/drivers/char/mmtimer.c
> > +++ b/drivers/char/mmtimer.c
> > @@ -669,6 +669,7 @@ static struct k_clock sgi_clock = {
> >  static int __init mmtimer_init(void)
> >  {
> >  	unsigned i;
> > +	int err = -1;
> >  	cnodeid_t node, maxn = -1;
> >  
> >  	if (!ia64_platform_is("sn2"))
> > @@ -680,7 +681,7 @@ static int __init mmtimer_init(void)
> >  	if (sn_rtc_cycles_per_second < 100000) {
> >  		printk(KERN_ERR "%s: unable to determine clock frequency\n",
> >  		       MMTIMER_NAME);
> > -		return -1;
> > +		goto out;
> >  	}
> >  
> >  	mmtimer_femtoperiod = ((unsigned long)1E15 + sn_rtc_cycles_per_second /
> > @@ -689,13 +690,13 @@ static int __init mmtimer_init(void)
> >  	if (request_irq(SGI_MMTIMER_VECTOR, mmtimer_interrupt, IRQF_PERCPU, MMTIMER_NAME, NULL)) {
> >  		printk(KERN_WARNING "%s: unable to allocate interrupt.",
> >  			MMTIMER_NAME);
> > -		return -1;
> > +		goto out;
> >  	}
> >  
> >  	if (misc_register(&mmtimer_miscdev)) {
> >  		printk(KERN_ERR "%s: failed to register device\n",
> >  		       MMTIMER_NAME);
> > -		return -1;
> > +		goto out1;
> >  	}
> >  
> >  	/* Get max numbered node, calculate slots needed */
> > @@ -709,16 +710,18 @@ static int __init mmtimer_init(void)
> >  	if (timers == NULL) {
> >  		printk(KERN_ERR "%s: failed to allocate memory for device\n",
> >  				MMTIMER_NAME);
> > -		return -1;
> > +		goto out2;
> >  	}
> >  
> > +	memset(timers,0,(sizeof(mmtimer_t *)*maxn));
> > +
> >  	/* Allocate mmtimer_t's for each online node */
> >  	for_each_online_node(node) {
> >  		timers[node] = kmalloc_node(sizeof(mmtimer_t)*NUM_COMPARATORS, GFP_KERNEL, node);
> >  		if (timers[node] == NULL) {
> >  			printk(KERN_ERR "%s: failed to allocate memory for device\n",
> >  				MMTIMER_NAME);
> > -			return -1;
> > +			goto out3;
> >  		}
> >  		for (i=0; i< NUM_COMPARATORS; i++) {
> >  			mmtimer_t * base = timers[node] + i;
> > @@ -738,7 +741,21 @@ static int __init mmtimer_init(void)
> >  	printk(KERN_INFO "%s: v%s, %ld MHz\n", MMTIMER_DESC, MMTIMER_VERSION,
> >  	       sn_rtc_cycles_per_second/(unsigned long)1E6);
> >  
> > -	return 0;
> > +	err = 0;
> > +out:
> > +	return err;
> > +
> > +out3:
> > +	for_each_online_node(node) {
> > +		if(timers[node] != NULL)
> > +			kfree(timers[node]);
> > +	}
> > +out2:
> > +	misc_deregister(&mmtimer_miscdev);
> > +out1:
> > +	free_irq(SGI_MMTIMER_VECTOR, NULL);
> > +	goto out;
> > +	
> >  }
> >  
> >  module_init(mmtimer_init);
> > diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
> > --- a/drivers/char/tpm/tpm.c
> > +++ b/drivers/char/tpm/tpm.c
> > @@ -1155,6 +1155,7 @@ #define DEVNAME_SIZE 7
> >  
> >  	if (sysfs_create_group(&dev->kobj, chip->vendor.attr_group)) {
> >  		list_del(&chip->list);
> > +		misc_deregister(&chip->vendor.miscdev);
> >  		put_device(dev);
> >  		clear_bit(chip->dev_num, dev_mask);
> >  		kfree(chip);
> > diff --git a/drivers/input/misc/hp_sdc_rtc.c b/drivers/input/misc/hp_sdc_rtc.c
> > --- a/drivers/input/misc/hp_sdc_rtc.c
> > +++ b/drivers/input/misc/hp_sdc_rtc.c
> > @@ -693,9 +693,13 @@ static int __init hp_sdc_rtc_init(void)
> >  
> >  	init_MUTEX(&i8042tregs);
> >  
> > +	INIT_LIST_HEAD(&hp_sdc_rtc_dev.list);
> > +
> >  	if ((ret = hp_sdc_request_timer_irq(&hp_sdc_rtc_isr)))
> >  		return ret;
> > -	misc_register(&hp_sdc_rtc_dev);
> > +	if (misc_register(&hp_sdc_rtc_dev) != 0)
> > +		printk(KERN_INFO "Could not register misc. dev for sdc\n");
> > +
> >          create_proc_read_entry ("driver/rtc", 0, NULL,
> >  				hp_sdc_rtc_read_proc, NULL);
> >  
> > diff --git a/drivers/macintosh/apm_emu.c b/drivers/macintosh/apm_emu.c
> > --- a/drivers/macintosh/apm_emu.c
> > +++ b/drivers/macintosh/apm_emu.c
> > @@ -520,6 +520,8 @@ static int __init apm_emu_init(void)
> >  {
> >  	struct proc_dir_entry *apm_proc;
> >  
> > +	INIT_LIST_HEAD(&apm_device.list);
> > +
> >  	if (sys_ctrler != SYS_CTRLER_PMU) {
> >  		printk(KERN_INFO "apm_emu: Requires a machine with a PMU.\n");
> >  		return -ENODEV;
> > @@ -529,7 +531,8 @@ static int __init apm_emu_init(void)
> >  	if (apm_proc)
> >  		apm_proc->owner = THIS_MODULE;
> >  
> > -	misc_register(&apm_device);
> > +	if (misc_register(&apm_device) != 0)
> > +		printk(KERN_INFO "Could not create misc. device for apm\n");
> >  
> >  	pmu_register_sleep_notifier(&apm_sleep_notifier);
> >  
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -856,6 +856,8 @@ static int __init tun_init(void)
> >  	printk(KERN_INFO "tun: %s, %s\n", DRV_DESCRIPTION, DRV_VERSION);
> >  	printk(KERN_INFO "tun: %s\n", DRV_COPYRIGHT);
> >  
> > +	INIT_LIST_HEAD(&tun_miscdev.list);
> > +
> >  	ret = misc_register(&tun_miscdev);
> >  	if (ret)
> >  		printk(KERN_ERR "tun: Can't register misc device %d\n", TUN_MINOR);
> > diff --git a/fs/dlm/user.c b/fs/dlm/user.c
> > --- a/fs/dlm/user.c
> > +++ b/fs/dlm/user.c
> > @@ -773,6 +773,7 @@ int dlm_user_init(void)
> >  	ctl_device.name = "dlm-control";
> >  	ctl_device.fops = &ctl_device_fops;
> >  	ctl_device.minor = MISC_DYNAMIC_MINOR;
> > +	INIT_LIST_HEAD(&ctl_device.list);
> >  
> >  	error = misc_register(&ctl_device);
> >  	if (error)

-- 
/***************************************************
 *Neil Horman
 *Software Engineer
 *gpg keyid: 1024D / 0x92A74FA1 - http://pgp.mit.edu
 ***************************************************/
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